While continuing to grow in popularity, portable or mobile electronic devices, such as cellular phones have also been growing in complexity. In addition to supporting wireless voice communication, devices such as the IPHONE multifunction device by Apple Inc., include additional functionality such as a built-in digital camera, digital music and movie file playback, and self-location capability. Multifunction devices now have built-in global positioning system (GPS) receivers that can compute the current geographic location of the device. This feature has been used in map applications, where the device can automatically find and display a route to a desired destination, from the current location calculated by the GPS receiver. In addition, there are current services offered for cellular phones that allow a user of a cell phone to alert a friend's cell phone about his current location. The service also allows the user to request that his cell phone show the location of previously identified cell phones (that have self-location capability).